Hibernate Session

Updated March 17, 2023

Introduction to Hibernate Session

There are many object-oriented programming languages having their own syntaxes and libraries while on the other hand, the entire data which we store in the backend is based on the relational model having entirely different protocols and syntaxes to be followed. Hibernate is one of the middleware platforms to bridge this gap. This middleware application I called Object Relational Mapping (ORM). We have various ORM tools such as Hibernate, IBatis, Toplink and many more. In this article, we will focus on Hibernate and its sessions.

What is Hibernate?

It is the ORM tool used to link and map the objects in the application layer to the database for JAVA programming language. It is built to handle the impedance mismatch between a typical programming language and the relational database. It is free of cost software with a GNU license, can be easily downloaded from the internet.

Hibernate is an extension of JAVA persistence API. It supports the Hibernate Query language (HQL). Hibernate’s major role is to link the JAVA objects and classes to the database classes via XML structure or JAVA annotations. Similarly, the datatypes of JAVA should be matched with the database’s datatypes so that there is miscommunication between two different systems. Hibernate can be used to extract the data using queries. It can generate the SQL calls and thereby mitigates manual errors and developer’s work. There are different inbuilt functions in hibernate for ease of use like:

load(), update (), get (), merge() : If we are sure that object exist then we use this function to load the hibernate object otherwise we use get() function. Update and merge functions are used to update the database records based on the current sessions already exist or we are totally fresh sessions for the transaction. There are many more functions like this to support hibernate.

What is the Hibernate Session?

It is a runtime interface between an application and Hibernates which is created on-demand. In other words, it provides the connectivity between your application and database. It offers various functions such as create, delete, get, update to operate on the database by using session methods that exist in four states namely: Transient, Persistent and Detached, Removed.

Hibernate has created to serve this purpose. It smoothly connects the database to java language irrespective of any database. It comes with flexible features and thus promoting flexibility of handling data over different platforms.

Methods of Hibernate Session

1. Save(): Save() method generates the primary key and inserts the record in the database. It is similar to the persist() method in JPA but it behaves differently in a detached instance by creating the duplicate record upon database commit.
2. Update():Update() is used to update the existing database record. It returns an exception if the record is not found or called in a transient instance.
3. saveOrUpdate(): It saves or updates the database based on the entity passed. It does not return an exception in the transient state but it makes the state to persistent during a database operation.
4. merge(): Values from a detached entity are updated to the database when the merge() is used by changing the detached entity to the persistent state.
5. delete(): Delete method works in persistent mode to remove the entity from the database. An exception is returned if no record is found in the database.

How to Create a Hibernate Session?

In order to create a hibernate session, we have to load hibernate dependencies in the library of the tool which you are using along with database connector. Once, these libraries are loaded we can establish the connection by creating a session using the session factory.

Let’s assume we have a table with two columns: Employee Id and Employee Name which should be updated.

Code Snippet:

import.org.hibernate.session // This way we hall import the hibernate class in the main program.
public class testclasshibernate //declaration of class.
{
public static void main( string[] args ) //The program;s main execution shall start from here.
{
testprogram = new program(); // Here the class is objectified and then this object is used as a reference to send the values like employee name and employee ID which needs to be imported into the database table.
program.setEmpId(101);
program.setEmpName(“User1”);
Configuration con = new Config().configure().addAnnotedClass testclasshibernate;
// Create session factory using configuration
SessionFactory sf1 = con.buildsessionfactory();
// Open session method gives the object of session.
Session s1 = sf.OpenSession();
// Opening Transaction
Transaction t1 = session.beginTransaction();
session.save(testprogram);
tx.commit();
}
}